package calculator.math;

import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;
/**
 * Created by liyf on 2015/3/30 0030.
 * 计算从 s到e的总和
 */
public class Count extends RecursiveTask<Integer>{

	private static final int THRESHOLD = 2;
	private int start;
	private int end;
	
	public Count(int start, int end){
		this.start = start;
		this.end = end;
	}
	
	@Override
	protected Integer compute() {
		int sum = 0;
		boolean canCompute = (end - start) <= THRESHOLD;
		if(canCompute){
			for(int i = start; i<= end; i++){
				sum +=i;
			}
		}else{
			//如果任务大于阈值，就分裂成两个子任务计算
			int middle = (start + end)/2;
			Count leftTask = new Count(start, middle);
			Count rightTask = new Count(middle +1, end);
			//执行子任务
			leftTask.fork();
			rightTask.fork();
			//等待子任务执行完，并得到其结果
			
			int leftResult = leftTask.join();
			int rightResult = rightTask.join();
			//合并子任务
			sum = leftResult + rightResult;
		}
		return sum;
	}

	public static void main(String[] args){
		ForkJoinPool forkJoinPool = new ForkJoinPool();
		//生成一个计算任务，负责计算1+2+3+4
		Count task = new Count(1, 100);
		//执行一个任务
//		Future<Integer> resultFuture = forkJoinPool.submit(task);
//		try{
//			System.out.println(resultFuture.get());
//		}catch(InterruptedException e){
//		}catch(ExecutionException e){
//		}
        forkJoinPool.invoke(task);
        System.out.println(task.getRawResult());
    }

}
